Quantitative assessment of creep damage in 9Cr-1Mo steel using nonlinear Lamb wave

Abstract

Using the nonlinear Lamb wave, this work investigated the damage resulting from microstructure evolution during the creep of 9Cr1Mo steel at 873 K in detail. At eight creep times, specimens of this steel were firstly prepared by the interrupted test to simulate various creep states, respectively. Then, the measurement of acoustic nonlinearity parameter, and microstructure observation were employed to characterize the resultant damage. The experiment results showed that the measured value of this parameter is strongly dependent upon the creep state. Meanwhile, the hierarchical microstructure of 9Cr1Mo steel evolves during creep. In order to conduct the quantitative assessment, both the analytical model of acoustic nonlinearity, and the kinetics of microstructure evolution were applied to calculating the acoustic nonlinearity parameter during creep. By comparison of the measured and calculated results, the predominated component of acoustic nonlinearity during the present creep of 9Cr1Mo steel was clarified successfully by the modeled microstructures. Above all, the present work provided an effective way to monitor and evaluate the creep damage quantitatively.